Climate crisis first, physics crisis next

From ‘CERN slashes experiment time next year by 20% as energy costs bite’, Physics World, October 12, 2022:

To avoid blackouts over the winter, France has launched a national plan to cut energy consumption by 10%. … Mike Lamont, CERN’s director for accelerators and technology, told Physics World that as a large industrial consumer of electricity, CERN feels its social responsibility. … As part of the planned energy savings in 2023, the physics experiments planned at accelerators such as the Super Proton Synchrotron (SPS) and the LHC will be curtailed by 20%. … In essence, a 20% reduction in operation time means 20% less data and although there will be attempts to make up time on missed work in future years, the proton-proton programme will be affected.

This article, and these measures, come at an interesting time. Particle physics today is at a difficult crossroads (I don’t want to repeat myself on this count, please see here for the reasons.) In this moment, a few collaborations have come forward with plans for what should be built next. Two of note are from CERN and from China. The former pitched for a ‘Future Circular Collider’ (FCC), a larger version of the Large Hadron Collider (LHC) (but built to achieve post-LHC goals in physics research), with a circumference of 100 km v. the LHC’s 27 km. China had published plans for a similar machine, called the ‘Circular Electron Positron Collider’ (CEPC), with similar operational characteristics and design outputs as the FCC.

The catch is that China published its plans a year before CERN did. Sure, these plans take many years to firm up, so it’s quite likely that both the CERN and the Chinese teams have been working on their respective plans for an almost equal amount of time, rendering China’s one-year jump quite irrelevant. It’s probably why Michael Benedikt, who heads the FCC plans at CERN, called China’s competing plan a validation of CERN’s instead of admitting a problem.

But the second issue is that both CERN and China have intended to build and run FCC and CEPC, respectively, as an international collaboration. This means only one of the two machines can be built. As Wang Yifang, director of the institute leading the CEPC, told The Wire in 2019, “The world may not be able to accommodate two circular colliders.” The world certainly won’t have the money for it. So whose machine will be built?

CERN made a case last month when two physicists found that the FCC would consume 3 MWh of electricity for every Higgs boson produced, while the CEPC would consume 4.1 MWh (in either collider’s ‘Higgs factory’ mode). This is almost intuitive considering CERN has the advantage of extending or repurposing, as the case may be, the infrastructure that already exists to support the LHC in service of the FCC. But on the flip side, China – while less energy-secure than Europe – has lower energy consumption per capita than most of the larger countries and can quite possibly – given the ostensible difference is only 1.1 MWh per Higgs boson – optimise its design further to meet the mark or even better CERN’s estimate.

But while I don’t know which way the international community will eventually swing, I’m glad the machines’ carbon footprints are in the picture: ultimately, the winning machine should have a lower carbon footprint at all costs. We can address the particle-physics crisis once we have tided over the climate crisis.